A measuring device for measuring structures on masks or substrates used for the production of semiconductors is disclosed in the lecture script “Pattern Placement Metrology for Mask Making” by Dr. Carola Bläsing. The lecture was given on the occasion of the Semicon conference, Education Program, in Geneva on Mar. 31, 1998. The basic principles of a coordinate measuring device are described in detail in this lecture script. For details regarding operation and structure of the coordinate measuring device, see FIG. 1 of the present patent application.
A measuring device for measuring structures on a transparent substrate may also be found in the published application DE 19819492. The measuring device includes an incident light illumination means, an imaging means and a detector means to image the structures on the substrate. The substrate is deposited on a displaceable measurement table, which may be displaced perpendicularly with respect to the optical axis. The position of the measurement table is determined interferometrically. Edge profiles of the structures are registered by the detector means. Based on the profiles, the positions of the edges of the respective structure may then be determined.
The patent specification DE 10047211 discloses a method and a device for determining the position of an edge of a structure element on a substrate. In the suggested method, first an image of the edge to be measured is taken. A one-dimensional intensity profile is generated from the pixels of the camera image. Then the edge position XK is determined with sub-pixel accuracy in the at least one intensity profile. Although this method finds the edges with very good repeatability, it is evidently not capable of correcting systematic errors caused, for example, by the imaging optics. A special category of these non-detected errors appears as position difference obtained between the measurement of an edge in 0° orientation of the structure and in 180° orientation of the structure at the same location.